I went ahead and did a test by reducing my timing. Wanted to let you all know the results and get your input. Following is what I know is true for runs before and after reducing my timing:

1. No KR ever at less than 100% TPS (approx. 91-99 MAP).

2. 12.1 AFR that is correct for all RPM's above 3600 but with minimal wideband data below 2000. Theoretically I should still be approx. 12.1:1. I am Richer than optimal to reduce KR.

3. timing at 100% TPS before reduction is 34-36 degrees at readout from Datamaster above 2800 RPM (not the tables but true readout).

4. 91 octane oxygenated gas used.

5. IAT around 101 degrees sometimes more. It gets real hot down here and even with my CAI, my inlet temps are always 10-15 degrees hotter than ambient.

6. Coolant temp. never above 188 degrees.

7. I have looked for obvious things such as headers banging against the frame, but I cannot say I saw every square inch of my underside and potential issues there.

8. Desensitized my new knock sensor by 30% as well as running higher grade insulated wire from the sensor to the PCM.

9. LT4 Knock Module.

Now what I did was reduce my timing by 10 degrees in the area of 85-100 MAP across the board from 400 RPM up. In the vicinity of 1400 to 1800 RPM, I test in 6th so as to give the KR plenty of time to kick in. In this area with reduced timing I was reading 5-7 degrees before retard and still would get KR coming on. Something I have always felt is a "bumping" coming through the clutch pedal when the KR would come on. However this bumping was a bit less during the reduced timing runs.

My KR was reduced at the higher RPM's, but never fully went away.

This to me seems like such minimal timing that there is no way for it to be real knock, but that is what I want to hear from all of you.

What is everyone's consensus on whether it is real or false? Any additional data you may need, just ask.

Just to let everyone know, I did feel a SOTP difference in power, but it was not major.

Ben

 

A couple of things I am considering is maybe I just have too high a IAT. Could that be so significant?

Also maybe if I have true knock, does reducing the timing by 10 degrees like I did really make that much of a difference? My guess is it should since that is the once thing the computer pulls when it sees knock.

 

Continuing on my testing, I have now put in 4 gallons 101 and 2 gallons 91 octane left over in the tank. This should be about 97.5 octane.

during run: IAT is about 89 but currently at 90% humidity.

Again, coolant never above 188.

Well, it seems my knock went away FINALLY after pulling 10 degrees across the board AND 97 octane.

Next step, put my timing back in and see how it responds.

Will let you know.

Pretty sure cooler plugs are in my future.

 

Keep us (me) updated on your outcomes. Been fighting with KR myself. Would like to see what it takes for you to remove or reduce the KR without having to run 101 race gas.

Michael

 

Ok, back at it.

I put 9 degrees of timing back in my car. Wanted to reduce my original timing by 1 degree hence why I put 9 back in.

So at WOT (90-100 MAP) I am running 32-36 degrees of advance from 2600 RPM up to 6000 RPM (again reading on the Datamaster).

IAT varied from 105 to 90 and again coolant never above 188.

KR was greatly reduced from before the testing.

My conclusion is this: taking the timing out by 10 degrees had less of an effect upon reducing KR than putting 101 octane in. The 101 octane is what made the difference.

The next step: empty my tank of 101 and put my crappy Phoenix 91 oxygenated in. Rerun the test, if the knock is the same as before I started, then I know I am on the right track.

So if this is the case, I will move to richening (going below 12 AFR) when in PE mode to compensate - remember my knock only happens at WOT. Doing this should cool the air as well as slow down the flame speed and by doing this accomplish what the 101 octane does (slow flame speed).

I will repost again in a few days on a progress report.

Ben

 

Keep it coming.

I noticed some improvement with mine using 101 octane. However, at $6.00 plus a gallon, it's not a viable fix. Course, I still got knock, WOT or regular driving, so there is still some false knock to deal with.

I've considered both retarding timing or richening the mixture. It's just contary to what should make power.

No one else may be posting , but I want to hear the outcomes. Thanks.

Michael

 

Don't think that more timing will make more power. Correct timing makes max power. being off by 2 or 3 degrees will not take much away from you power but may improve your knock.

The relationship to correct timing and power is nonlinear. at close to correct, a change of 2 - 3 degrees off of perfect will have a small effect on power. However, if you were already waaay off and took 3 more degrees, you would see much more of a drop off in power.

This holds true for AFR. Now other can give their opinions on perfect AFR but we should see best power with AFR of 12.6:1 or so. However being off by much will not affect it that much. I ran back to back dyno's with a wideband. First pull was 12.8 AFR 2nd was 13.3. the HP loss was 1% going to 13.3. This should hold true on the rich side. your *** cannot feel 4 HP, so be safe.

You may or may not have false knock. Have you checked your AFR with a wideband?

Thanks for the post interest. It is also helping me keep a diary of sorts that I can go back to in the future and see what I said, did etc.

Ben

 

I'm not totally following your post. Maybe you could send me a datamaster file?
Also, not sure why you'd want to add more fuel when you've already got plenty. Odds are the knock retard is due to too much timing on your crappy gas.
Set the timing map up to where you get 32* all the way up and see where you get knock count and go from there.
Just seems to me that you're going about this backwards...but I might not be understanding yet.

 

Dan,

One of the things I have learned is that adding fuel reduces the flame propagation speed just like high octane gas does. This is why I want to lower my AFR even more.

Would be glad to send you my file if you think it would help. As for why I am doing it this way is because I want to know if this is false or real knock.

My intent was just to find this out and thus why I just took 10 degrees out across the board at high MAP (the only place I get knock). Well this proved that it was still there in a reduced amount. This did not prove to me either way if I had false or real knock.

Then I put in the 101 octane and my knock was eliminated. This now proves that I have real knock and from here, I can then do what you suggest.

Another thing, my knock is not consistent at any RPM. it varies at WOT from 1500 to 6000 whenever it decides to show up. Dan, if you have a suggestion on this timing thing, can you give me complete details? Like maybe trying 32 deg and then at 4000 jump to 35 to see if that causes knock exactly at 4K?

Thanks for the input.
Ben

 

Ben,
I feel you have the same problem I have with high temps and high humidity. I'm in Florida. Not that this solves your problem, but just wanted to let you know what I have found on my logging. I was also only getting KR over 4400 rpms in 2nd gear and higher (A4) and only at 95+ map readings. As load on the engine got higher at WOT the KR got a littler higher, 2nd gear a little, 3rd gear even more after 4400 rpms, etc. What I've noticed with repeated runs is I only get the KR during the day when it's 90 degrees or so, if I run at 7 in the moring or 10 at night when it's 75 degrees I have no KR. I ran a mixture of 4 gallons premium to 1 gallon Toluene which gives an octane rating somewhere in the upper 90's and ran it during the day. I had no KR. This led me to believe that the high heat/humidity was knocking my octane rating down. I did put my timing back to stock in the 95 and 100 map columns (lowered it 2 degrees) and it help lower my KR during the day. I also experimented with AFR from 12.5 to 13.1 and it didn't seem to make a difference on KR. Although this isn't a solution I just wanted to assure you the heat/humidity you have there in Arizona is not your friend. I wish there was some test's out there that showed temperature versus octane ratings and what effect it had. There could be and I haven't found them. I'm curious to see what changes the Wisconsin climate has on my readings since I will be moving there in two weeks. Higher sea level, lower temps/humidity.

 

Thanks for that reply.

I did learn by reading that humidity plays a part in reducing the "octane" of the combustion mixture. How much, I wish I knew and in regards to IAT's, well, we all know that is a factor.

Now if we could just get an analysis saying something like 10% change in humidity will change you octane by 1 point. I am not suggesting this is fact, just trying to explain what I wish we had.

I will try and do a bit of a search on this subject around the Net.

 

Wow Ben...you're really getting into this!
Not sure if I'd be much help here at all. I'm not all that interested in why things happen, just eliminating them.
Only thing that seems strange is that you took out 10* and were still getting a little bit of knock retard, right? So at 25-28ish degrees you were getting knock?

 

Dan,

Correct. I was getting KR with mid to high 20's timing in my car with caca Phoenix 91 oxygenated gas.

I took at page out of your TC file you sent me BTW and I put all my timing to base 32 degrees (including compensation by the computer with that "mystery" timing).

Tonight I put in crappy 91 and I will tell you all the results. This time, I plan on being a bit more scientific.

Also, I purchased a set of plugs 2 ranges colder that I intend to put in and test before the weekend is over.

This thread may get pretty long

Ben

 

Ben I officially hate you.
After reading this post I decided to go outside and play a little with the program in my car.
I'm getting a consistent knock retard right at 4500rpm. I've got the tables set up to have 34* and as soon as it hits 4500..wham. Retard.
I took out some timing and it was still there.
So I decided that I was going to start adding a little fuel to the pe vs rpm table and guess what...?
O2 voltage starts dropping as I added fuel...and the knock retard started to go away. On one wot pass in 3rd I'll have nothing...then 30 seconds later on another I'll get 3 or 4 degrees of retard and then shift into fourth and have nothing.
I'm starting to think my car doesn't like 3rd gear.
I guess I'll add a little more fuel to the car and see if I can get this retard to go away.
I want to get the car on a dyno (even if it is stock), but I want to wait and take the GN and the Z and do them both at once. That'll be fun!

 

All your input has cause me to think and I did some things.

Ok here are the results of testing:

Humidity: 38%

IAT: 95 - 105 F

Gas: 91 Octane "up to 15% MTBE" per the tag on the pump.

Coolant: Less that 189 F

Timing: 32 Degrees at WOT (as read in Datamaster) throughout my RPM range from 2800 to shutdown.

I gave the car 5 miles to clear out the remaining high octane in the fuel line and testing occurred for another 10 miles.

The only place I saw any retard was at almost always 5700 RPM. Every single time I got to this RPM, KR would show up.

The only other intermittent time I saw it was around 4500 but that was random and not as strong.

Now the big thing that confused me is the fact that I said I had KR even after i reduced timing by 10 degrees while using 91 octane. Well, after a closer look at those old files, I in fact had retard at the areas of just lower than full MAP where my timing would be in the 40's. So my original analysis was a bit flawed.

I gave up on testing in the range of 1300 to 1800 RPM WOT in 6th. I know that I will never do that while driving and thus will never have such issues as I had finding the KR that occured in this area.

Next step: Find where I do get KR consistently by upping timing by 3 degrees across the board.

I still want to get those plugs in also.